1. Field of the Invention
The present device relates to an air bag device in which an air bag inflates in front of and comes in contact with a person at the time of the sudden acceleration of a vehicle.
2. Background Information
An air bag device has been proposed which protects a person in a vehicle by an air bag being inflated in front of the person during the rapid deceleration of a vehicle (Japanese Patent Application Laid-Open Nos. 60-248454, 60-248455, 60-248456 and 60-248457).
With this air bag device, when there is rapid deceleration of a vehicle, a ball in an air bag activation device moves by being subjected to inertial force causing a drive shaft that is in contact with the ball to rotate. An igniting pin in engagement with the drive shaft is released and collides with a percussion cap which combusts a gas generating material thereby inflating the air bag.
A safety device is disposed in this kind of an air bag device so that an air bag does not inflate carelessly in case an impact is erroneously imparted to the air bag device when it is installed or removed. The safety device prevents the ball from moving via the drive shaft by preventing the drive shaft from rotating by bringing a lengthy portion of a coiled spring in contact with the drive shaft. The drive shaft is in contact with the ball.
The following is a description of the operation of releasing the safety device with reference to FIG. 10. First, a slide member 102 is pressed, and by pushing up a release pin 104 axially (in the direction of an arrow Y of FIG. 10), a lock shaft 106 is moved axially. Then, a lengthy portion 108A of a coiled spring 108 in contact with the bottom of a ring groove 106A formed in the lock shaft 106 is moved from the ring groove 106A to a peripheral portion 106B of the lock shaft 106 due to the axial movement of the lock shaft 106. By this, the lengthy portion 108A of the coiled spring 108 rotates counterclockwise in FIG. 10 (in the direction of an arrow X of FIG. 10) and withdraws from the locus of rotation of a drive shaft 110, and thus, a ball 100 becomes movable.
Due to this structure, the surface pressure between the lock shaft 106 and the coiled spring is high, which requires unconventional, anti-friction treatment such as oil lubrication or surface finishing, which further results in the high cost of manufacturing the product.